Shown are the variables in the longitudinal regression analysis over 9 years, with
joint erosion score as the dependent variable and TNFA -308G > A or TNFA -308G > A × year as primary dependent variables. Year2 allows for a non-linear course of joint progression score over time. The analysis
was corrected for gender, and time-averaged 28-joint disease activity score (DAS28),
rheumatoid factor and age were not confounders.